Collective focusing of an intense pulsed ion beam

Abstract

Under the assumptions of quasineutrality and small perturbation to the applied solenoidal magnetic field, collective focusing of a neutralized, intense pulsed ion beam injected into a solenoidal magnetic field region is demonstrated. The focal point was observed to occur within the solenoidal magnetic field and was at a location in between the single-particle electron and ion focal points. The focused beam current density was an order of magnitude above the 20 A/cm2 of the incident beam. The experimental results were found to be in good agreement with a theoretical model developed under the above assumptions. The presence of background plasma or a conducting liner was observed to remove the collective focusing, confirming the physical picture of the theoretical model.